Imaging micro-spectrometer with space-variant adaptive dispersion incorporating a MEMS mirror array

We report the design, fabrication, and testing of a novel imaging micro-spectrometer system for the 500-1000 nm wavelength range. The space-variant design incorporates a linear array of MEMS mirrors in order to vary the dispersion spatially on a pixel-by-pixel basis. A planar-optics geometry is used so that the spectrometer optics are contained on a single piece of bulk fused silica. The object to be investigated is imaged onto a linear array of tilting MEMS mirrors that define the spectrometer slit. Each individual MEMS mirror tilts to send the light to one of three blazed gratings of differing dispersive powers. Depending on the wavelength and selected grating the spectral resolution is between 5 and 20 nm. The collimating and focusing mirrors of the spectrometer are fabricated in standard photoresist via grayscale photolithography with a custom high-energy beam-sensitive (HEBS) photomask. A reflow at 70 degrees Celsius for 40 hours is necessary to achieve near diffraction-limited performance. The blazed gratings are fabricated in SU-8 via direct-write electron-beam lithography. Spectrometer results with a variety of lasers and gaseous discharge tubes are presented and indicate that system performs as expected.